Glass fibers containing a dual polyester resin size

ABSTRACT

A glass fiber sizing composition for the reinforcement of resin matrices is provided which comprises a homogeneous aqueous composition of two polyester resins. The first polyester resin is a water solubilized condensation cross-linkable, polyester resin, insoluble in aromatic solvents. The second polyester resin is insoluble but dispersible in water but insoluble in the first polyester resin. Thus, when the second polyester is blended with a water solution of the first polyester, a dispersion is produced. In this dispersion the water and the first polyester form the continuous phase and the second polyester forms the dispersed phase. A plasticizer and two silane coupling agents are also incorporated into the sizing composition. The first coupling agent is provided to promote adhesion between the glass fibers and the resin matrix and the second silane coupling agent is employed in the sizing composition to control the wetting of the glass fibers by the first silane coupling agent. A thermoplastic polymer of sufficiently low molecular weight is employed to impart pressure sensitive adhesive characteristics to the sizing composition. Glass fibers sized with the sizing composition of the invention have found particular utility when incorporated into resin matrices which are utilized as molding compounds.

REFERENCE TO CROSS-RELATED APPLICATIONS

This is a division of application Ser. No. 606,272, filed Aug. 20, 1975,which is a division of application Ser. No. 512,646, filed Oct. 7, 1974,now U.S. Pat. No. 3,936,285.

FIELD OF THE INVENTION

This invention relates to a glass fiber sizing composition, a method ofapplying the sizing composition to glass fibers during formation, andglass fibers for incorporation into molding compounds.

BACKGROUND OF THE INVENTION

A glass fiber strand is composed of a multitude of fine glass filamentswhich are formed by being drawn at a high rate of speed from moltencones of glass at the tips of small orifices in a bushing such as shownin U.S. Pat. No. 2,133,238. During formation, the filaments are coatedwhile moving at a speed on the order of 1,524 to 6,096 meters per minutewith a size which contains a binder to give the strand integrity andworkability for any standard textile or reinforcement use. The size alsocontains a lubricant for the filaments to prevent damage to the strandby abrasion of the individual filaments against each other or againsthandling equipment during processing.

The attenuative force supplying the high speed drawing force to form thefine glass filaments is usually provided by a winder or a wheel puller.A winder is typically a rotating drum on which a paper tube (formingtube) is placed. As the fibers are drawn and gathered into strands, thestrands are collected on the forming tube which rotates with the winder.The wheel puller, as an attenuative device, is primarily a pair oftractive, juxtaposed surfaces which pull the strand and project ordirect it to a collecting apparatus.

Glass fibers in the form of strand, both continuous and chopped, mat androving having found utility in the area of reinforcing resinousmatrices.

Roving is formed by mounting a plurality of glass fiber forming packageson a creel or support and gathering the strands from the separatepackages in parallel, to form a rope or roving. This braided rope orroving is wound on a rotating drum to collect the roving. The roving soproduced has a plurality of uses. It can be chopped and separated intoseparate strands to form chopped strand. It can be woven to form wovenroving or it can be used by merely unwinding and impregnating it withresin for applications such as filament winding and pultrusion. Rovingin whatever form utilized imparts substantial strength to resincomposites reinforced therewith.

Roving which has been chopped to form chopped strand has found utilityin the area of glass fiber reinforced molding compounds. In one area ofglass fiber reinforced molding compounds, glass fibers which have beenchopped are dispersed through a thickened, polymerizable polyesterresinous material. This thickened resinous material with the glassfibers dispersed therethrough has a substantial viscosity in order thatit may be handled by conventional techniques for such molding compounds.

In order to obtain a glass fiber roving which is acceptable forutilization in not only the molding compound area but also anyreinforcement area the formation and processing of the roving mustpresent as few problems in production as possible. The glass fiberstrand, to form the roving must have integrity in order to tolerate theprocessing necessary in forming the roving and in subsequent unwindingand chopping. Also when the strands are gathered in parallel to form theroving, it is desirable that they cohere to each other to form a uniformrope. However, this adhesion between strands in the roving should not betoo great because unwinding of the roving and passage of the rovingthrough the chopping apparatus will be difficult if too much tack isimparted to the strand and the roving formed therefrom.

The strands within the roving must also be capable of being dissociatedfrom each other during the chopping of the roving so that they mayuniformly disperse throughout the molding premix.

Another problem associated with the forming of glass fibers is themigration of the binder and sizing composition when the fibers are driedafter formation. The aqueous sizing composition is coated onto thefibers as they are formed and the strand, which consists of gatheredfibers. The strand is then wound on a forming package. These formingpackages are subsequently dried in an oven and if desired, under reducedpressure. During this drying process, the solids of the sizingcomposition have a tendency to migrate from the inside of the package tothe outside of the package. Therefore, the strands which are on theoutside of the package have substantially more sizing compositionthereon than the inside strands of the package. This causesnonuniformity of the performance of the strands and roving formed fromthe strands. Hence, it is desirable to have a sizing composition whichis nonmigratory and produces a uniform distribution of sizingcomposition on the strands throughout the forming package.

Along with the processing properties, the strand must also demonstrateexcellent adhesion to the resin matrix to effectively reinforce theplastic article formed therefrom. Therefore both the chemical andphysical properties of the glass fiber strand in the resin matrix aredetermined primarily by the sizing composition placed on the strandduring formation.

The instant invention provides a sizing composition and a glass fiberroving formed from strand with the sizing composition thereon which isuseful in the production of fiber reinforced molding compounds. Further,this invention provides composites formed from such molding compoundswith improved strength and uniformity.

Further, the instant invention provides a sized glass fiber strand whichis easily processed both during formation and subsequent to formation,in that the sizing composition is nonmigratory. Still further, theinvention provides a strand which is easily formed into roving, ispliable, chops and disperses easily, and imparts adequate wet-out andwet-through characteristics to SMC and BMC formed therefrom.

Further advantages of the instant invention will become apparent withthe further description thereof.

BRIEF DESCRIPTION OF THE INVENTION

The sizing composition of the instant invention comprises two polyesterresins. The first polyester resin is a water solubilized condensationcross-linkable unsaturated polyester resin salt which is substantiallyinsoluble in aromatic solvents when cross-linked. The second polyesterresin is an unsaturated water dispersible polyester resin insoluble inthe first polyester resin. Thus, when a solution of the first polyesterresin salt is formed and the second polyester is added thereto, adispersion is formed with the first polyester resin salt and waterforming the continuous phase and the second polyester resin forming thedispersed phase. A plasticizer is included in the composition to provideflexibility to the strand and to control the coalescence of the polymerson the strand to form a uniform fiber. The coupling agent which is usedto couple the glass to the resin matrix is a dual-coupling agent system,both coupling agents being silanes. The first silane is highly adhesivein nature and promotes adhesion between the glass fibers and the resinmatrix. The second silane coupling agent has substantially lesserbonding characteristics than the first silane coupling agent, butcontrols the wetting of the glass fibers by the first silane couplingagent. Finally, a thermoplastic polymer of sufficiently low molecularweight to impart pressure sensitive adhesive characteristics to thesizing composition is included. Typically the sizing solution is appliedto glass fibers during formation at a total solids content of about 2 to20 percent by weight, preferably 9 to 17 percent by weight.

DETAILED DESCRIPTION OF THE INVENTION

By "water soluble resin" is meant that a mixture of water and resinyields a single phase homogeneous solution. By "water dispersible resin"is meant that a mixture of water and resin yields a two-phasehomogeneous mixture. By "substantially insoluble" is meant that a givensolvent will form a heterogeneous mixture with a given resin.

Typically a first water soluble polyester resin is incorporated in thesizing composition in an amount from about 1 to 10 percent by weight ofthe total solids. This polyester resin can be formed from carboxylicacids and polyhydric alcohols by techniques known to those skilled inthe art. In all cases, however, an ethylenically unsaturated carboxylicacid or anhydride such as maleic anhydride, maleic acid, fumaric acid orthe like must be a major component in the formation of the polyestercondensation product in order to impart adhesive characteristics betweenthe dispersed strand and the resin matrix. It is believed that thisadhering characteristic is imparted by the interpolymerization of thesize on the strand and the resin matrix through the double bonds in thesize and the resin. A typical water soluble unsaturated polyester resinhas a polycarboxylic acid having more than two carboxyls per molecule asa component in the synthesis thereof. Therefore, because a portion ofthe carboxylic acids employed in the synthesis of the polyester resinhave a functionality of greater than 2, a substantial amount of freecarboxyl will be available for subsequent dispersion of the polyesterresin in water by salt formation and condensation cross-linking thusproducing substantial insolubility of the size in aromatic solvents whenthe size is cross-linked. The solubilization is accomplished by means ofthe addition of a volatile amine which is capable of forming a salt withthe pendant carboxyl groups on the polyester chain. Typically, triethylamine, dimethyl ethanol amine, ammonia and the like can be utilized insolubilizing the polyester resin provided the solubilizing agent can bedissociated from the sizing composition and evaporated at acceptablecuring temperatures and times, i.e., 120° to 177° C. from 2 to 24 hours.

The curing time and degree of curing of the polyester can be adjusted bythe selection of the nitrogenous base used to solubilize the polyesterresin. A high boiling amine, i.e., dimethyl ethanolamine, will requiresubstantial time and temperature to fully dissociate from the strand,hence if complete cure of the size is not desired, complete dissociationof the amine will not be conducted. If a low boiling solubilizing base,e.g., ammonia is used, cure times and temperatures can be substantiallyreduced.

This first water solubilized polyester resin provides a glass fiberstrand with good wet out.

The excess carboxyl functionality of the polyester resin necessitatescare in its synthesis in order to avoid cross-linking by condensation.The acid functional polyester resin is condensation polymerized to apoint near its gel or cross-linking point so that when the glass fiberstrand with the size thereon is subjected to heat, the polyester resinwill condensation cross-link with itself or other hydroxyl functionalitypresent in the solids of the sizing composition. Typically, trimelliticanhydride or trimellitic acid is used in the synthesis of the polyesterresin along with maleic anhydride and a polyhydric alcohol to obtain thesolubilization and condensation cross-linkable properties of thepolyester.

Further, other saturated dicarboxylic acids may be used in thecondensation of this first polyester resin. However, only a minor amountof the difunctional, saturated dicarboxylic acid may be used in orderthat no substantial detraction of unsaturation or pendant carboxylationin the polyester is obtained which will detract from the watersolubility and the condensation cross-linking properties of the finalsizing solution.

The second polyester resin which is water dispersible but insoluble inthe first polyester resin is incorporated at a level of 2 to 10 percentby weight of the sizing composition. Typically, this polyester is formedfrom maleic, fumaric or the like previously mentioned unsaturatedcarboxylic acids or anhydrides and a polyhydric alcohol such as thosepreviously discussed. Further, non-free radically polymerizabledicarboxylic acids may be utilized in the synthesis of the polyester ina mole ratio which does not detract from the capability of the secondpolyester to bond the glass with the resin matrix to be subsequentlyapplied to the surface of the glass fibers. Further, the secondpolyester resin imparts nonmigrating characteristics to the size. Thissecond polyester resin is believed to provide good wet through to theglass fiber strand. This good wet through is provided by retarding thewet out with the polyester molding compound of the glass. By having apolyester resin in the sizing composition which has an affinity for thepolyester molding compound to be reinforced therewith, extreme intimacyof contact between the resin and the glass will be obtained.

The plasticizer is added to the sizing composition to impart pliabilityto the glass fiber strand and the roving associated therewith for easein processing during forming, fabrication of the roving, chopping of theroving prior to incorporation into the resin matrix and to aid in thecoalescence of the sizing composition solids into a continuous film onthe strand. Generally, the plasticizer is incorporated into the sizingcomposition at a level of 2 to 10 percent by weight based on the totalsizing solution. A particularly advantageous plasticizer is tricresylphosphate. Other plasticizers known to those skilled in the art may beutilized so long as they impart the necessary properties of flexibilityand processability necessary to the strand and roving formed therefromand to aid in the coolance of the sizing solids. Typical otherplasticizers are dioctyl phthalate, dibutyl phthalate, ethylortho-benzol benzoate, and the like.

The combined coupling agent system of the invention utilizes twocoupling agents both preferably silanes. The first coupling agent is onehaving amino functionality which can be designated by the generalformula

    NH.sub.2 R--Si--(OR.sub.2).sub.3

wherein R is an alkylene radical having from two to eight carbon atomsand R₂ is a lower alkyl radical or hydrogen; the lower alkyl radicalhaving one to five carbon atoms, preferably one or two carbon atoms.

The second silane coupling agent characteristically has a reactivemoiety thereon which is free radically polymerizable such as acrylate,methacrylate, alkyl, vinyl or the like. A particularly advantageousacrylate coupling agent is gamma-methacryloxypropyltriethoxysilane.However, other unsaturated coupling agents such as vinyl triethoxysilane, vinyl trimethoxy silane and the like may be utilized as thesecond coupling agent.

Typically, each silane coupling agent is incorporated into the sizingcomposition at a level of 0.1 to 5 percent by weight based on the totalweight of the sizing solution.

The thermoplastic polymer is incorporated into the sizing composition toprovide a strand which is sufficiently tacky to adhere the strandstogether to ease in the production of the roving. However, much tack ofthe strand should be avoided so that the roving can be readily unwoundand processed through the chopping device without filament breakage.

Typical thermoplastic pressure sensitive polymers useful forincorporation into the size are low molecular weight acrylic resinssynthesized from the homopolymerization, copolymerization orinterpolymerization of methyl methacrylate, ethyl acrylate,2-ethyl-hexyl acrylate, butylacrylate, styrene, vinyl acetate and thelike. Other thermoplastic polymers may be used so long as they provide asufficient tack level to the glass fiber strand. One polymer has beenfound to be particularly useful in the size of the invention. Thispolymer is a PAISLEY ® 76-3663 which is a vinylacrylic copolymeremulsion supplied as a 50 percent ± 2 percent water emulsion having anaverage particle size of 0.5 micron, a viscosity of 1500 to 2000centipoises and a pH of 6 to 7.

In preparing the sizing composition of the invention, the watersolubilized polyester resin solution is diluted further with water. Tothis water solution is added the second polyester resin to form adispersion. The water and the first polyester resin which has beensolubilized forms the continuous phase of the dispersion and the secondpolyester resin forms the dispersed phase of the dispersion. Thisphysical relationship between the first polyester resin and the secondpolyester resin prevents the migration of the sizing composition duringdrying. A completely water soluble sizing composition migrates to thesurface of the forming package during drying because the water carriesthe sizing solids with it as it travels to the surface of the package.Typically when a water soluble size is used, a variation in loss onignition of the strand varies between 0.6 percent on the interior of theforming package to 3.5 percent on the exterior of the package.

By having the one polyester resin in a continuous aqueous phase of adispersion and a second polyester resin in the dispersed phase of thedispersion, the variation in loss on ignition of the strand is about 2.2on the interior of the forming package to 2.6 on the exterior of thepackage.

Further, the pH of the mixture of the first and second polyester resinshould be controlled to be between 3 and 7 and more preferably 6 to 7.At pH ranges of 8 and above, it has been found that the second polyesterdissolves in the water and solubilized polyester phase of the dispersionthus forming a solution hence distracting from the nonmigratorycharacteristics of the sizing composition.

Generally there are two types of chemically thickened molding compoundswhich have found major utility for making articles formed therefrom.These are bulk molding compounds (BMC) and sheet molding compounds(SMC). Both BMC and SMC are formed from a thickened polyester resinhaving a polymerizable monomer therein. Typically the polyester resin isthickened with magnesium oxide or magnesium hydroxide. A relatively lowviscosity is encountered on initial mixing of the magnesium oxide withthe unsaturated polyester-monomer solution. After aging this solution,it substantially thickens to form a compound having a viscosity muchlike a dough (i.e., 10 to 70 million centipoise).

The polyester may also contain fillers such as clay, talc, calciumcarbonate, silica, calcium silicate and the like. Additionally, pigmentsmay be added to impart color to the molding compound.

The unsaturated polyester resinous material is based on an unsaturatedcondensation polyester blended with an alpha, beta ethylenicallyunsaturated monomer and may further include a thermoplastic polymer.Typically the polyester is used in amounts ranging from 20 to 80 partsby weight of the total resinous system and preferably in amounts rangingfrom 25 to 65 parts by weight. This class of unsaturated polyesters initself is not unique and methods of preparing them are well known. Thesepolyesters are synthesized by the condensation of an unsaturateddicarboxylic acid or anhydride or mixtures thereof with a polyhydricalcohol. Further, other carboxylic acids not having free radicallypolymerizable functionality may be utilized so long as enoughunsaturated carboxylic acid is condensed into the polymer chain toprovide adequate cross-linking with the ethylenically unsaturatedmonomer. Preferably, maleic anhydride, maleic acid or fumaric acid areamong the preferred unsaturated carboxylic acids or anhydrides. However,other unsaturated acids may be used, for example, chloromaleic acid oranhydride, tetrahydrophthalic acid or anhydride and the like. Typically,the nonfree radically polymerizable carboxylic acids or anhydrides maybe used in an amount up to about 25 mole percent based on the totaldicarboxylic acid and/or anhydride incorporated into the condensationpolymer. Examples of such nonfree radically polymerizable dicarboxylicacids or anhydrides are phthalic, isophthalic, terephthalic, succinic,adipic, sebasic, methyl succinic, hexahydrophthalic and the like.

The polyhydric alcohols useful in preparing the unsaturated polyesterresin to be used in the resinous material are the dihydric alcohols suchas propylene glycol, dipropylene glycol, diethylene glycol,1,3-butanediol, 1,5-tetramethylene glycol and the like, the trihydricalcohols such as trimethylol propane, trimethylol ethane, clycerol andthe like and the tetrols such as pentaerythritol and the like. Typicallythe condensation polymers have a molecular weight of about 500 to 5,000and preferably from about 700 to 2,000 and have an acid number of lessthan 100 and more preferably less than 70.

The ethylenically unsaturated monomer must be copolymerizable with theunsaturated polyester resin hereinbefore described to provide across-linked final product. Typically, styrene and vinyl toluene are thepreferred ethylenically unsaturated monomers. Other monomers may beutilized such as the acrylic monomers, preferably the lower alkyl esters(i.e., 1 to 10 carbon atoms) of acrylic acid; aromatic monomers such aschlorostyrene and the like; and in some cases difunctional ethylenicallyunsaturated monomers may be utilized such as diethyleneglycoldiacrylate, 1,3-butane diol dimethacrylate and the like. Typically themonomer is used at a level of 20 to 80 parts by weight of the totalsystem and preferably between 35 to 75 parts by weight.

In order to free radically polymerize and thereby cross-link thepolyester resin, free radical initiators such as benzoyl peroxide,tertiary butyl peroctoate, ditertiary butyl peroctoate, cyclohexanoneperoxide, ditertiary butyl peroxide, lauryl peroxide and the like, mustbe utilized. Usually a concentration of 0.1 to 3 percent by weight basedon the resinous system is incorporated to provide adequate curing.

Further, to impart minimum shrinkage during the curing cycle, e.g., tominimize the density difference between the cured resinous moldingcompound and the liquid resinous molding compound, thermoplasticpolymers are normally incorporated into the molding compound. These areusually acrylic polymers such as polymethylmethacrylate,polyethylmethacrylate, polybutylacrylate, polymethylacrylate,polystyrene and the like, and copolymers thereof. Further, vinyl halidepolymers such as vinylchloride or vinylchloride - vinylacetatecopolymers may be utilized and also the cellulosic polymers such ascellulose acetate butyrate, or cellulose acetate propionate. Also, vinylacetate polymers and ethylene vinyl acetate copolymers may be used toreduce shrinkage.

Bulk molding compound (BMC) is prepared by mixing in a high shear mixerthe unaged polyester monomer solution having the thickening agent andthe other ingredients therein along with chopped glass fiber strand orroving. This high shear mixer homogeneously disperses the glass fibersthroughout the resinous phase of the composition thus forming a bulkmolding compound which, after thickening on aging, can be sliced intodesired shapes such as cubes and the like and placed in a press to formarticles of the desired design.

Sheet molding compound (SMC) is formed by first coating the polyesterresin premix, with a thickening agent therein, on a nonadhering surfacesuch as a polyethylene sheet. A uniform film of the desired thickness isapplied to the sheet as it travels on a conveyor belt. Chopped glassfiber roving, strand or mat is uniformly disposed onto the polyesterresin coating. A second nonadhering substrate is coated with the samepolyester resin premix and brought in contact with the first polyesterresin with the glass fibers thereon. Subsequent to the joining of thetwo polyester coatings, the sandwich is kneaded with a plurality ofrollers having varying configurations to uniformly distribute the glassfibers throughout the polyester premix. The sandwich is then taken up ona roll and can be used in subsequent molding operations.

The glass fiber chopped strand which is dispersed across the surface ofthe first polyester resin premix coated substrate is normally formed bytaking a plurality of roving packages, threading the ends of each rovingpackage through a plurality of guide eyes into a chopping device whichchops the roving to the desired length, and disperses the glass onto thepolyester resinous coated substrate in the form of chopped glass strand.

In order to form an acceptable bulk or sheet molding compound, glassfibers must have an acceptable size on their surface. The solubility ofthe glass fiber sizing composition in ethylenically unsaturated aromaticsolvents can affect the final properties of the molded product. Ininstances where severe shear is necessary to disperse the glass fibersthroughout the polyester premix, it is desirable to have a sizingcomposition which is substantially insoluble or totally insoluble in thepolyester resin premix to prevent filamentation of the strand, i.e., tokeep the filaments in discrete bundles. When severe shear is notnecessary to homogeneously disperse the glass fiber strand throughoutthe polyester premix during compounding and molding, increasedsolubility of the size on the strand can be tolerated. Further, andespecially in SMC, the individual strands of fibers are to behomogeneously dispersed throughout the premix in order to form a uniformsheet molding compound.

If the sizing composition on the glass fibers is not properlyformulated, the fibers will not disperse uniformly through the resinpremix. The characteristic of the molding compound formed from thepolyester and glass fibers which describes the homogeneity of the premixcomposite is called "wet through" or "flow through". It is desirable tohave a high degree of wet through in a sheet molding compound in orderthat the final physical properties of the molded articles and theprocessability thereof be at their maximum level. On the other hand, itis also desirable that the glass fiber strands be wet out duringcompounding which means that the resin encapsulates the glass fiberstrands and no bare glass is visible throughout the formed moldedcompound. Wet out during compounding is a measure of the apparentintimacy of contact between the resin matrix and the glass fiber strand.If the glass fibers are not immediately wet out following compoundingand it is not expected that they will wet out on aging due to theincreasing of the viscosity of the compound, there will be adverseeffects on the processability, molding characteristics and surfaceproperties of the final molded article.

The following examples will further elucidate the concept of theinvention.

EXAMPLE I (Polyester A)

Four moles of propylene glycol, 1 mole of maleic anhydride, and 1 moleof isophthalic acid were charged to a reaction vessel equipped with astirrer, a heating apparatus, an inert gas inlet, a thermometer todetermine the temperature of the reaction and a thermometer placed atthe top of a distillation column to determine the temperature of theeffluent from the reaction mixture. The above ingredients wereesterified to an acid value of 8.2. One mole of trimellitic anhydridewas added thereto and reacted with the above formed polyester until acure time of less than 30 seconds at 220° C. was obtained. The resin wasstoichiometrically neutralized with an aqueous triethyl amine solution.

The following table demonstrates the progress of the reaction:

                                      Table I                                     __________________________________________________________________________        Kettle                                                                            Effluent  Inert Gas                                                   Time                                                                              Temp.                                                                             Temp.                                                                              Distillate                                                                         Sparge Rate                                                                          Acid                                                                             Cure Time                                         (hrs.)                                                                            (° C.)                                                                     (° C.)                                                                       (mls.)                                                                            (liters/hr.)                                                                         No.                                                                              (sec.)                                                                              Remarks                                     __________________________________________________________________________    0   RT  RT   0    14.16  -- --    Materials charged, heat on.                 1   180 98   1st drop                                                                           14.16  -- --    First water off.                            3   195 97   52   14.16  -- --    --                                          4.7 210 91   69   28.32  -- --    Increase sparge.                            6.3 215 74   80   28.32  20.2                                                                             --    --                                          8.6 216 39   82   28.32   8.2                                                                             --    --                                          8.8 216 35   83   14.16  -- --    Cool lower sparge.                          9   205 --   --   14.16  -- --    Charge TMA, empty distillate.               9.25                                                                              195 97   1st drop                                                                           14.16  -- --    Charge completed.                           9.9 202 90   29   14.16  -- --    No vortex - reduce heat.                    10.8                                                                              192 60   40   14.16  63.2                                                                             42    --                                          11  192 55   41   14.16  -- 27    Heat off. Begin to blend                                                      resin into distilled water                                                    and appropriate amount of                                                     triethylamine.                              __________________________________________________________________________

The final resin had an acid number of 57.2, a cure time of 28 seconds, anonvolatile content of 30 percent, a Gardner-Holt viscosity of A-1 at25° C., a Gardner color of 1, and a pH of 7.4. Of particular importanceis the cure time of the final resin so that when such a resin isincorporated into the sizing composition and the fibers are sizedtherefrom, subsequent heating will condense the free carboxylic acid inthe polyester resin. The cure time is determined by heating thepolyester at 200° C. and measuring the time required for gelation.Generally in the above type of polyester, an acid value from 30 to 90,preferably 40 to 60, is necessary to obtain proper solubilization andcross-linking of the sizing composition.

Polyester B

A polyester resin was synthesized in the conventional manner using 6mols of maleic anhydride, 4 mols phthalic anhydride, 10.5 mols ofethylene glycol, 0.2 mole of CARBOWAX ®1540 w, a high molecular weight,polyethylene glycol. The components were condensed to an acid valuebetween 18 and 26 and a Gardner viscosity of 0 to Q at 60 percent resinsolids in ethyl CELLUSOLVE ®.

Seventy-five parts of the above polyester resin are mixed with 25 partsof ethyle CELLUSOLVE ®, 0.1 part of 2,6-ditertiarybutyl paracresol and0.002 part of methyl quinone.

PREPARATION OF THE SIZE

75.71 liters of water were charged to a mix tank equipped with anagitator and 2,682 grams of alpha-aminopropyltriethoxy silane were addedto the mix tank with agitation. 75.71 liters of water were charged to anemulsification tank equipped with a high shear EPPENBAUCH ® agitator.1,722 grams of ABEX ® 18S, an anionic emulsifier having a solids contentof 35 ± 170 and pH of 7.5 to 8.5 at 25° C. sold by Alcolar ChemicalCorporation, 1,722 grams of tricresol phosphate, and 38,499 grams ofpolyester B were charged sequentially to the emulsification tank withagitation. The agitation was continued until a homogeneous emulsion wasobtained. 37.85 liters of water were charged to a premix tank equippedwith an agitator, 73,547 grams of polyester A were charged to the premixtank with agitation. To a second premix tank was charged, withagitation, 2 grams of acetic acid, 56.78 liters of water and 2,682 gramsof alpha-methacryloxypropyltriethoxy silane. The contents of theemulsification tank, the first premix tank and the second premix tankwere charged sequentially to the mix tank and agitated until homogeneousat which time 1,344 grams of vinyl acrylic thermoplastic polymer, 50percent solids in water was added to the mix tank after being dilutedwith 7.5 liters of water. The total volume of the size was brought to378.5 liters. The size had a pH of 6.7 ± 2, a solids content of 17 ± 2percent.

The following table shows the composition of the sizing solution:

                  Table II                                                        ______________________________________                                               Ingredient        Amount (%)                                           ______________________________________                                        Polyester resin A        5.84                                                 Polyester resin B        7.66                                                 Anionic surfactant       0.45                                                 Tricresol phosphate      0.45                                                 Gamma-aminopropyltriethoxysilane                                                                       0.58                                                 Gamma-methacryloxypropyltrimethoxysilane                                                               0.58                                                 Methyl methacrylate copolymer                                                                          1.78                                                 Deionized water          82.66                                                ______________________________________                                    

The above sizing solution provides a glass strand with about 2.2 to 2.6percent by weight of the dried size composition on the strand based onthe total weight of the glass and with the dried residue of the sizingsolution thereon.

Glass fibers drawn from a bushing were sized with the above sizingcomposition during formation. The individual sized filaments weregathered into strands and collected on a forming tube mounted on an20.32 cm collet which was rotating at 4100 revolutions per minute. Aplurality of forming packages as above formed were dried in an oven at133° C. for 11 hours. Fifteen of these forming packages were mounted ona creel, braided into roving, and collected on a rotating spindle toform a roving ball. The ends of 22 of such roving balls were threadedinto the chopper of a SMC machine.

A sheet molding compounding resin having the following composition wasused to form the sheet molding compound:

                  Table III                                                       ______________________________________                                               Ingredient        Amount                                               ______________________________________                                        Resin - 1:1 propylene maleate polyester                                                                65%                                                  Styrene                  35% (60 parts)                                       Thermoplastic acrylic polymer                                                                          30 parts                                             (polyvinylacetate)                                                            Calcium oxide filler     150 parts                                            Peroxide catalyst benzoyl peroxide                                                                     .5 part                                              Thickening agent - Magnesium oxide                                                                     .65 part                                             Release agent            5 parts                                              Pigment (black)          .26 part                                             ______________________________________                                    

The above SMC formulation was applied to the surface of a polyethylenesheet at a uniform coating thickness. The glass fiber roving was choppedand the strand inherently separated from the roving and uniformlydispersed upon the coated polyester. The same polyester was coated on asecond polyethylene sheet and the two resin surfaces were joinedtogether to form a sandwich. The sandwich was kneaded with a pluralityof rolls to uniformly mix the glass fiber chopped strand and thepolyester molding compound. The sandwich was then wound on a roll.

Several sheet molding composites were made in accordance with the abovemethod using different thicknesses of polyester coating on thepolyethylene sheet and adjusting the linear speed of travel of thepolyester fiber glass sandwich. A linear speed of 152 centimeters perminute with a density of 3417 grams per square meter produced a sheetmolding compound with a 100 percent wet through which means that theglass fiber strand was homogeneously mixed throughout the polyestermolding compound. Also the strands had complete encapsulation by thepolyester molding compound and no bare glass was observed. At a linearspeed of 670 centimeters per minute at a density of 5,858 grams persquare meter, the wet through and wet out were still maintained at 100percent. At a linear speed of 609 centimeters per minute at a density of8,298 grams per square meter, observation showed that the wet throughwas 90 percent and the wet out was 60 percent on a relative basis.

EXAMPLE II

A commercial glass fiber roving was used in sheet molding compoundutilizing the same polyester for the molding compound in the same methodas above described. Sheet molding compound made from the roving ofExample I and the commercial roving were molded and tested for flexuralstrength, flexural modulus, tensile strength and Izoid notched impact.

The following table illustrates the superiority of the instant glassfiber sized roving in comparison with the commercially used sheetmolding compound using glass fiber roving. The molded articles producedwith the roving of the instant invention are designated as roving A andthose produced by the commercial roving as roving B.

                                      TABLE III                                   __________________________________________________________________________                                                 TENSILE                                          GLASS              FLEX MODULES                                                                            STRENGTH IZOD IMPACT                   CHARGE SHAPE                                                                            CONTENT                                                                              FLEX STR.   NEWTONS/  NEWTONS/ (NOTCHED)               ROVING                                                                              CM × CM                                                                           %      NEWTONS/METER.sup.2                                                                       M.sup.2 × 10.sup.6                                                                M.sup.2 × 10.sup.6                                                               NEWTONS                 __________________________________________________________________________    A     11.43 × 26.61                                                                     17.3   580,527     50.18     158,644  488.9                   B               19.9   476,670     50.55     168,974  415.3                   A               29.7   1,147,403   63.09     450,475  934.1                   B               32.0   977,691     58.6      398,455  800.6                   A               34.7   1,313,426   68.99     520,205  448.7                   B               35.3   132,818     70.10     441,252  944.8                   SMC at 3661 g/m.sup.2                                                         2.54 cm × 46.64 cm moulded panel dimension                              A     17.78 × 17.78                                                                     25.0   1,125,267   62.72     453,796  822.0                   B                      1,110,509   59.03     361,561  800.6                   A     11.42 × 26.67                                                                            1,005,361   55.34     383,697  741.9                   B                      878,077     59.03     339,424  709.9                   A     17.78 × 33.02                                                                            966,622     55.34     411,368  1056.8                  B                      881,766     59.03     332,046  816.7                   A     21.59 × 39.37                                                                            962,933     59.03     354,182  1121.0                  B                      914,971     62.72     324,667  827.3                   SMC at 3417 g/m.sup.2                                                         22/.86 cm × 40.64 cm moulded panel dimensions -                         A     17.78 × 17.78                                                                            1,036,721   59.03     391,076                          B                      885,456     51.65     287,773                          A     12.7 × 25.4                                                                              1,365,078   70.10     586,614                          B                      1,103,130   66.41     461,175                          A     29.21 × 29.21                                                                            922,350     55.34     317,288                          B                      771,084     55.34     265,636                          SMC SMC at 3417 g/m.sup.2                                                     30.48 cm × 30.48 cm moulded panel dimensions                            A     17.78 × 7.78                                                                             1,180,608   62.72     376,329  864.7                   B                      1,106,820   62.72     332,055  822.0                   A     10.54 × 26.67                                                                            894,679     55.34     354,192  779.3                   B                      774,774     55.34     280,402  731.3                   A     17.78 × 30.48                                                                            889,145     55.34     335,744  774.0                   B                      872,543     59.03     298,849  763.3                   A     21.59 × 39.37                                                                            787,686     59.03     306,228  790.0                   B                      760,016     59.03     273,023  816.7                         SMC at 8299 g/m.sup.2                                                   __________________________________________________________________________

As is shown in Table III glass fibers formed by the practice of theinvention impart superior physical properties to molded sheet moldingcompounds with such fibers incorporated therein.

Glass fibers formed with the sizing composition of the invention havefurther utility in reinforcing thermoplastic resins.

Further, glass fibers formed with the sizing composition of the instantinvention have found use in the areas of preform roving, filamentwinding continuous glass fiber mat, chopped strand mat and pultrusion,showing superior reinforcing characteristics.

As can be recognized by those skilled in the art, variations incomponents specified in the example and ranges thereof may be madewithout departing from the scope of the invention. Therefore, theinvention is limited only as is set forth in the accompanying claims.

I claim:
 1. Glass fibers having thereon the dried residue of a sizingcomposition comprising:a water solubilized, condensation,cross-linkable, first unsaturated polyester resin, said polyester resinsubstantially insoluble in aromatic solvents when crosslinked; a secondunsaturated water dispersible and insoluble polyester resin, said secondpolyester resin being insoluble in said first polyester resin in a watersolution and said second polyester resin preventing the migration ofsaid sizing composition; a plasticizer; a first silane coupling agent topromote adhesion between said glass fibers and said resin matrix; asecond silane coupling agent to control the wetting of said glass fibersby said first silane coupling agent; a thermoplastic polymer being ofsufficiently low molecular weight to impart pressure sensitive adhesivecharacteristics to said sizing composition; and a major amount of water.2. Glass fibers having thereon the dried residue of a sizing compositioncomprising 1 to 10 percent by weight of a water solubilizedcondensation, cross-linkable, first unsaturated polyester resin, saidpolyester resin substantially insoluble in aromatic solvents whencrosslinked;2 to 10 percent by weight of a second unsaturated waterdispersible and insoluble polyester resin, said second polyester resinbeing insoluble in said first polyester resin in a water solution andsaid second polyester resin preventing migration of said sizingcomposition; 2 to 16 percent by weight of a plasticizer; 0.1 to 1.5percent by weight of a first silane coupling agent to promote adhesionbetween said fibers and said resin matrix; 0.1 to 1.5 percent by weightof a second silane coupling agent to control the wetting of said glassfibers by said first silane coupling agent; 1to 6 percent by weight of athermoplastic polymer being of sufficiently low molecular weight toimpart pressure sensitive adhesive characteristics to said sizingcomposition; and a minimum of 80 percent by weight of water.
 3. Theglass fibers of claim 1 wherein the sizing composition producing thedried residue is at a pH of less than 7.